Solution:
At 1st convert km/h to m/s. 1 km = 1000 m, 1 h = 3600 s, 1 km/m = 1000/3600 = 5/18 m/s
Initial velocity = 75 * 5/18 = 20.8 m/s
The car’s velocity decreases from 20.8 m/s to 0 m/s at the rate of 0.5 m/s each second. We have the final velocity, initial velocity, and the acceleration.
Now according to the equation determine the distance.
vf^2 = vi^2 + 2 * a * d
a = -0.5 m/s^2
0 = 20.8^2 + 2 * -0.5 * d
so d = 431.64 m
since we have the final velocity, initial velocity, and the acceleration. Use the following equation to determine time.
vf = vi + a * t
0 = 20.8 – 0.5 * t
Solve for t = 41 seconds
(c) the distance travels by it during the first and fifth second are.
d = vi * t + ½ * a * t^2
d1 = 20.8 * 1 – ½ * 0.5 * 1^2 = 20.55 m
The easiest way to the distance for the 5th second is:
d = vi * t + ½ * a * t^2, a = -0.5
d5 = 20.8 * 5 – ½ * 0.5 * 5^2 = 91.5 m
d6 = 20.8 * 6 – ½ * 0.5 * 6^2 = 106.8m
d6 – d5 = 15.3 m
this is the required solution.
